Recent years have seen significant advances in the technology of constituting a minute space for conducting a chemical reaction in such a space. One method of constituting such a minute space is use of photolithography which is a technology most frequently used in the production of a semiconductor. A microfluidic device can be constituted by forming a groove in a silicon substrate by means of photolithographic process, and adhering another substrate over the groove to thereby form a minute channel for receiving a fluid which is actuated by the device. Various proposals have been made for use of such microfluidic device in chemical production (for example, Analytical Chemistry, 74, 3112-3117 (2002)) and chemical analysis (for example, Analytical Chemistry, 73, 2112-2116 (2001)).
Chemical reactions utilizing an enzyme immobilized on microparticles have been investigated for various enzymatic reactions, and typical processes include the process wherein microparticles having an enzyme immobilized thereon are suspended in the solution for chemical reaction, and the process wherein such microparticles are used by filling in a column having a diameter much larger than the microparticles. Also known in the art as a process utilizing a chemical reaction that takes place at the interface between the microparticle and the liquid is the purification of a particular molecule by using microparticles wherein microparticles having immobilized protein A or the like are filled in a column for use as an antibody purification column.
In the meanwhile, biological molecules are typically measured by immobilizing a probe molecule in each well of a micro-well plate, and dispensing the sample in each well to measure the biological molecule captured by the probe molecule. In the case of ELISA, for example, an antibody is used for the probe molecule to quantitatively measure the biological molecule in the sample. In this case, an antibody molecule which has affinity for the biological molecule is immobilized on the plate, and after capturing the biological molecule by the antibody molecule, a high sensitivity measurement by enzymatic chemiluminescence is conducted using an enzyme-labeled secondary antibody having affinity for the biological molecule.
Another method for measuring a biological molecule that is in development is a method wherein a plurality of probe molecules are immobilized in different areas of the solid phase to measure the biological molecule captured by each probe molecule. An example is the DNA chip wherein a plurality of probe DNAs are immobilized on a planar substrate of glass or the like for detection of nucleic acid molecules. In the case of this chip, a solution containing a fluorescence-labeled nucleic acid molecule is placed on the chip for hybridization and the amount of analyte nucleic acid molecule in the solution is determined by detecting fluorescence on the chip. The methods often used for producing such a DNA chip include spotting of the DNA probe on a slide glass (for example, Science, 270, 467-470 (1995)), and use of a photolithographic process and the sequential synthesis of the DNA by a photochemical reaction (for example, Science, 251, 767-773 (1991)). Also proposed is a protein chip wherein a plurality of proteins are simultaneously measured (for example, Analytical Biochemistry, 278, 123-131 (2000)). Devices using not the planar surface but a channel formed in the device have also been proposed, and exemplary such devices include the one wherein a DNA probe has been immobilized in the capillary (for example, Japanese Patent Application Laid-Open No. 11-75812), and a probe array wherein probe-conjugated microparticles have been arranged in the interior of the capillary (for example, Japanese Patent Application Laid-Open No. 11-243997).
Processing a large amount of sample in a short time is generally difficult in the chemical reaction system where molecules immobilized on the solid phase are reacted with the molecules in the solution, or in the chemical analysis system where molecules immobilized on the solid phase capture the molecules in the solution by chemically reacting with such molecules and the captured molecules are measured.
To be more specific, the methods mentioned in the Prior Art section including the method wherein microparticles are filled in a column, the method using a micro-well plate, and the method using a DNA chip have been associated with the difficulty of establishing the sample flow while promoting reaction in the minute space, and as a consequence, improvement in the chemical reaction efficiency and reduction of the process time have been difficult.